This invention relates to an optical scanner and the like. In a conventional optical scanner, brilliance control of a light source is usually done by darkening and filtering processes performed in the lamp tube and charged coupled device (CCD). The purpose of the darkening process is to maintain an evenly distributed brightness in axial direction of a scanning lamp tube, i.e. to make the scanning document with equal illuminance at every spot in the horizontal direction. The purpose of the filtering process is to adjust the light intensity of the light source according to the contrast difference of the scanning document to achieve a better scanning quality.
It is well-known that the light intensity of a fluorescent lamp is lower at the lateral sides. The conventional darkening process is to provide make-up light at the two lateral sides of a fluorescent lamp. It needs a specially designed reflector to obtain the desired results. When the object being scanned is a transparency, because the picture and image on a transparency usually have a wide variety of quality or contrast difference, the light intensity or the brilliance of the light source needs constant adjustment so as to obtain a better scanning result. The conventional approach is to equip a manual switch on the scanner to adjust the brightness of the light source. This increases the costs. The scanning quality and results are not always satisfactory since a manual switch has only a limited number of adjustment selections due to its physical or mechanical constraints. Thus there is a need for improvement on the control of brilliance of light source in an optical scanner.